User interface for a display screen



FIG. 1 is a front view of a user interface for a display screen showing the new design; and,

FIG. 2 is an enlarged front view thereof, the user interface is shown separately for clarity of illustration.

The broken line showings of the display screen and the other features form no part of the claimed design. 

The ornamental design for a user interface for a display screen, as shown and described. 